When this problem first reared its ugly head - almost 2 years ago shortly after buying the boat, we did run 10 micron Racor 500 filters. There was a lot of biomass in the fuel at that time, and we were having to change blackened Racors AND engine filters frequently. Now the engine filter stays clean and the 2 micron Racors more slowly darken. We still change the Racors before the filter pressure gauge moves out of the black "OK" zone. Im convinced at this point that running 10 micron Racors would only mean much more frequent engine filter changes.

Wow, it sounds like you've still got a lot of some sort of contamination in the fuel. Have you tried a Bahamian filter to see what's going in your tank before it disappears down the hole? Maybe you're getting bad fuel. Filters that darken and clog that quickly should be an alarm bell.

There was a huge amount of biomass in the tank when we bought the boat. Due to tank access problems, it was not possible to clean the tanks spic and span, and some crud was left in them to hopefully break up and filter out.

I asked the mechanic who did the polishing/tank cleaning a year or so ago if pickup screens would have prevented the filter clogging problem, and he told me that screens were not a good thing to have. I hope that meant that our pickups did not have screens. I'll check, though I don't think that is the problem. As for more bad fuel - certainly possible, though we have moved the boat enough that we've never filled from the same place twice. I'll see if the fuel pump has its own screen that might be clogging. The mechanic at our current berth has suggested running it from a jug, we'll give that a try too.

I think somebody mentioned this already, but a totally blocked fuel tank breather ........ A couple of hours of fuel consumption would result in a a fuel tank vacuum .......enough to result in a net fuel starving. Could you try running with fuel filler cap slightly loose or even off to avoid vacuum in fuel tank to test this theory.

I had the same problem except we are talking 8 hours or so until the engine would shut down. It turned out to be long fiberglass strands in the fuel line that were caught in the elbows. As time went on they would slowly compress until they choked off the fuel. Once the pressure was off they would spring back after ten minutes or so and everything would be fine.

I had the same problem except we are talking 8 hours or so until the engine would shut down. It turned out to be long fiberglass strands in the fuel line that were caught in the elbows. As time went on they would slowly compress until they choked off the fuel. Once the pressure was off they would spring back after ten minutes or so and everything would be fine.

Safari, very interesting experience, can you clarify a bit more?

Are the "fibreglass strands" part of the braid embedded in the rubber fuel hose, or just stray strands that by accident got into the fuel tank?

To completely shut the fuel line, it must be a little "crows nest" of strands?

What causes them to compress over time (heat or just continuous fuel flow or other) ?

Thanks.

Note to "vet222": Good point on breathers, but the OP had stated in his original post that he'd tried that.

Are the "fibreglass strands" part of the braid embedded in the rubber fuel hose, or just stray strands that by accident got into the fuel tank?

To completely shut the fuel line, it must be a little "crows nest" of strands?

What causes them to compress over time (heat or just continuous fuel flow or other) ?

Thanks.

Note to "vet222": Good point on breathers, but the OP had stated in his original post that he'd tried that.

The fiberglass came from the tank. Little Harbor 38s have built in fiberglass tanks. A few of our elbows had masses of the fibers caught because they couldn't make the turn. The continuous flow would slowly compress them over time until no fuel could flow.

We also had material from the old foam inspection port gasket that had rotted and was floating around the tank. This would cause the engine to stop very eruptly. When the engine stopped from the fiberglass strands it was slow.

I would think about checking the fuel lines and elbows and also pump the fuel tank and clean it.

Hi, this is my first post. I have much the same problem with my universal m4-30.
Starts normally, runs for half hour or so then abruptly dies. Have to wait 30+ min to restart.
This is new this year at start of season, - new filters installed this spring. Very little water evident in primary favor. Some fuel line connections were trimmed and retightened which improved the running time but still had a failure after 40 min. I suspect air incursion in one of the fuel lines , maybe a clogged screen at the tank, or starving due to vacuum in the tank.
Does anyone know if an islander 37 had a screen at the tank outlet? I am not even sure there is a vent for the fuel tank.
BTW was the original poster's problem resolved?
Thanks for any ideas.

sounds like air leak or fuel pick up problem..mine did that until we fixed the pick up so it wont allow the bubblel to get into engne...30 mins runtim pulling ancor then ded at rocks--hooyaahh..doesnt cut it---fix your fuel pick up and find all air leaks...

sounds like you are using the fuel in the racor then it quits.....pick up..... have fun and happy sails.

Boracay said it before but didn’t explain, sorry not reading all posts.
Don't overlook the fuel return, fuel being returned is used for flushing/cooling/lubricating, if it gets hot thru static heat it would probably vapor lock some where. It should return to day tk if not theres your problem, if your return is fine but only goes to suction pipe, getting hot on suction side not good.
If your fuel tank is getting warm, your suction head is getting stretched your suction lift pump not up to it in theory you would starve the engine thru vapour lock with mild fuel temperature rise and yet everything else is fine.
Some people I know installed a above engine Daily fuel tk, good idea. Other than that aneal your copper washers at the banjos and breather, have a look at suction lift pump.
If that doesn't help pull out the injector and see if you have a trumpet that just fell off, that would also give time delay slowdown.